The present invention relates to the automatic production of filter paper bags containing products such as tea, chamomile and similar herbs designed to be immersed in a liquid in order to make infusions for diverse uses, for example, as beverages or for medicinal purposes.
More specifically, the invention relates to a machine for the production of filter bags made by folding and sealing webs of heat-sealable filter paper and where the thread connecting the chamber that contains the infusion product to the pick-up tag is wound around the outside of the containment chamber itself and partly enclosed, in the form of one or more closely gathered up loops, between the flaps of the pick-up tag which have been folded onto each other.
The apparatus embodies a method which, together with the filter bag made according to the method, is described in prior Italian patent application IT BO 2002A000013 in the name of the same Applicant as the present, This method essentially comprises the steps of:
forming a row of filter bag pickup-up tags by cutting a web of suitable material at regular intervals;
feeding a continuous thread above the row of tags to form, above a flap of each of the consecutive tags, a row of first loops of thread;
associating the first loops of thread with the tags;
feeding a web of heat-sealable filter paper over the continuous thread and over the tags connected to it;
pushing a portion of the thread through the web of filter paper in such a way as to form a second loop projecting from the face of the filter paper web opposite the face adjoining the tags;
folding the web of filter paper onto itself so that its edges, which were initially opposite one another, are juxtaposed in such a way as to gradually form a substantially flattened tube of filter paper;
depositing a succession of charges of the infusion product on the filter paper web, before the tube is definitively formed;
sealing the longitudinal edges of the tube;
making transversal sealed joins upstream and downstream of each tag, so as to delimit a succession of closed pouches, each containing a charge of the infusion product;
securing the portions of thread between the transversal sealed joins to the tube;
cutting the flattened tube, lying in a substantially horizontal position, into consecutive lengths;
folding each length of tube onto itself about the join between the two consecutive pouches in such a way that the two pouches are mutually superposed;
joining the pouches by a top join; and
trimming the corners of the top join.
The main aim of the present invention is to provide an automatic machine embodying the method described above and capable of making the filter bags on an industrial scale.
Another aim of the invention is to provide a machine that produces the filter bags at a very high speed and whose operation is reliable.
A further aim of the invention is to produce filter bags wrapped individually in sealed, protective envelopes.
Yet another aim of the invention is to enable the filter bags, with or without envelopes, to be collectively packaged in cartons.